[FEATURE] Add Per Page Internationalization

With these additions single pages and single posts can be rendered in a different language. Specify the language in the post directive or in the documents metadata.

Find a complete description in my new blog ( : - )) which exactly is the use case for the new feature:
http://mbless.de.local/blog/2014/09/19/ablog-per-page-i18n.html

Yippieh!